The remotes are so simple its complicated. If the solder points aren't broken on them, its either the battery is low and its not powering it like it should, or it possibly might need to be reprogrammed. Ive seen them sometimes get grime under the buttons and cause issues, make sure you clean the contact points well too.

If the contacts are clean, solder isn't broken on battery connections, and good battery, try reprogramming or replace the remotes. simple as that. Ive never had any gm car come in with a bad or messed up receiver, its always the remotes (not that the receiver COULDN'T go bad, just haven't ever seen one).